1. The Field of the Invention
The invention relates to balloon catheters, and more particularly to a balloon catheter wherein the balloon, after inflation, can be automatically sealed and detached from the catheter.
2. The Prior Art
Balloon catheters have been available since about 1950 and have been used in such diverse medical techniques as arterial emboli extraction, venous thrombectomy, and removal of biliary calculi. Furthermore, percutaneous balloon catheters have been developed for interventional angiography and have been utilized to control hemorrhage, operative angiography, conventional embolectomy, vena cava occlusion, and intentional vascular thrombosis or dearterialization.
In recent years, there has been considerable interest in developing detachable balloon catheters for use in surgical procedures that involve vascular occlusion, e.g., occlusion of carotid-cavernous sinus fistulas and other arterio-venous malformations, particularly those involving intracranial circulation. Heretofore, repair of cerebral aneurysms and arteriovenous fistulas has required radical brain surgery, despite the fact that such surgery is necessarily dangerous and complicated. For example, it is not uncommon for such surgery to result in the destruction of valuable portions of the brain in order to get to the aneurysm, often resulting in partial paralysis or loss of some vital autonomic function. Hence, heretofore a patient afflicted with a cerebral aneurysm or fistula was often required to choose between the risk of loss of his life if he elected not to undergo surgery, or the risk of a future of less than full use of his faculties in the event that he elected surgical correction of the problem.
Recently it has been found that radical surgery can be eliminated and inoperable aneurysms can be corrected through a safe and efficient technique involving a detachable balloon catheter. The catheter is "snaked" through the artery to the point of the aneurysm, the balloon is inflated until it occludes the vascular lumen, and the balloon is detached so that the catheter can be removed. The detached balloon is employed to obstruct the venous outflow tract and to artificially reconstitute the damaged wall of the cavernous segment of the involved carotid artery. Unfortunately, routine utilization of this valuable technique has been thwarted by the lack of a reliable apparatus.
The problem which has faced those skilled in the art is how to inflate the balloon after it is in position and then reliably seal the balloon and detach it from the catheter while it remains in position without damaging the balloon or the surrounding tissue. Although various attempts to solve this problem have been made by those skilled in the art, to data there has not been devised an apparatus and method that have fully succeeded in achieving a solution to this problem.
For example, one prior art approach to the problem has been to inflate the balloon, leave the catheter attached to the balloon extending through the artery, seal the catheter, and tie the catheter off at a place remote from the aneurysm, such as the point of entry into the artery. See, e.g., Prolo et al., "Balloon Occlusion of Carotid-Cavernous Fistula: Introduction of a New Catheter," 7Surgical Neurology 209-13 (April 1977).
The technique has several significant drawbacks. Chief among them is that the catheter must remain in the artery as long as the balloon is to remain in position, thereby obstructing the flow of blood in the artery. This may be particularly disadvantageous since the artery involved is often the carotid artery--the source of blood flow to the brain. Leaving the catheter in the artery also opens up the possibility of several other medical problems caused by a foreign object in the delicate portions of the brain. Also, researchers have had trouble in keeping such a balloon inflated over a long period of time.
Another prior art approach to the problem has been to use a double lumen catheter design in order to detach the balloon from the catheter. In this approach a small latex balloon is tied to the end of a catheter by thin latex threads under tension and a second catheter is provided surrounding the first inner catheter. The inner catheter is manipulated into position and the balloon is inflated. The outer catheter is then positioned snugly against the base of the balloon and the inner catheter is pulled backwards, separating the balloon from the inner catheter while the tightly wound latex threads at the base of the balloon keep it inflated. See generally, Fierstien et al., "Complete Obliteration of a Carotid Cavernous Fistula With Sparing of the Carotid Blood Flow Using a Detachable Balloon Catheter," 9 Surgical Neurology 277-80 (May 1978); Debrun et al., "Endovascular Occlusion of Vertebral Fistulae by Detachable Balloons With Conservation of the Vertebral Blood Flow," 130 Radiology 141-47 (January 1979).
Although this technique has advantages as compared to leaving the catheter attached to the inflated balloon, several disadvantages have been observed. Unless a solidified filler, such as silicone, is used to inflate the balloon, it has been found that the fluid will gradually diffuse out of the balloon, collapsing it within two or three weeks after implantation. However, solidified filler is difficult and awkward to work with and results in a permanently hardened balloon. Since the catheter is initially inserted into the balloon during inflation, when the catheter is removed the volume of the balloon decreases by a volume representing the dead space of the catheter. Other problems have been observed, including premature separation of the balloon from the catheter, migration or other unwanted effects secondary to the permanent implantation of the balloon, and the risk of bursting of the balloon during the inflation step.
Another approach that has been tried is the use of a balloon that is attached to the tip of a double lumen catheter by means of a metal tube. The distal half of the metal tube is tapered so that it can penetrate into an elongated, solid neck portion on the balloon. After the balloon is inflated, the metal tube can be withdrawn by using the outer catheter and the thickened rubber portion of the balloon will self-seal. See Liliequist et al., "Occlusion of the Carotid Artery Using Catheter With Detachable Balloon In Pigs," 20 Acta Radiologica Diagnosis 100-04 (January 1979); Laitinen et al., "Embolization of Cerebral Vessels With Inflatable and Detachable Balloons," 48 J. Neurosurgery 307-08 (February 1978).
The problems encountered with this design are similar to those discussed above. The main problem has been leakage of the balloon, which may not be apparent until as long as one or two weeks after implantation. Furthermore, there have been cases of balloon damage during passage through the outer guiding catheter, and there have been instances of rupture of the balloon after the catheter had been withdrawn.
Yet another approach to the problem has been to use a balloon that is attached to the catheter by a C-shaped spring clamp. See, e.g., U.S. Pat. No. 4,085,757. After the balloon has been inflated to seal the vascular lumen, additional fluid is injected into the balloon increasing the pressure until the balloon squirts off of the end of the catheter. The C-spring clamp then closes off the opening in the balloon left by the retracted catheter.
Again, this approach has resulted in certain drawbacks. In particular this design results in an excessive pressure exerted on the walls of the vessel at a point near the aneurysm or fistula in order to detach the balloon. Furthermore, an accurate determination of the ultimate size of the balloon is difficult and movement of the balloon during the detachment step is possible (as well as injury to the vessel during such movement).
In summary, the problems discussed above have posed significant obstacles to the development of a detachable balloon catheter that is safe, simple, and effective in its operation, thus preventing routine diagnostic and/or therapeutic use of the balloon catheter despite the otherwise significant advantages that may be obtained through such use.